Many industries require reliable processes for depositing thin coatings of polymeric materials on selected substrates. One means of performing this process is via the vacuum flash evaporation of monomer fluids. A continuous liquid flow of monomer fluid is atomized into a continuous flow of liquid droplets. The droplets are in turn continuously vaporized upon contact with a heated surface that is maintained at a temperature at or above the boiling point for said material, but below the temperature at which said droplets would undergo decomposition and/or polymerization before vaporizing. The vapor may in turn be deposited onto a substrate and subsequently polymerized. This process is detailed in U.S. Pat. No. 4,954,371, incorporated herein by reference.
There is also a related need for polymer composite layers containing ions or salts. Such layers may exhibit a variety of characteristics, such as increased ion conductivity, that may render them superior for specific uses to polymers that consist of polymerized monomer alone. Laminate structures having at least one polymer layer have also been shown to be useful in a wide variety of applications including, but not limited to, electronic devices, such as the formation of anodes for use in electrochemical cells such as Li—S batteries, packaging materials, and solar reflectors.
Initially, those skilled in the art avoided the use of the vacuum flash evaporation method for the formation of polymer composite layers. Conventional wisdom dictated that the temperature required to evaporate salts was too high to permit the inclusion of salts in the evaporation of monomers according to the flash evaporation method. Nevertheless, the use of vacuum flash evaporation method offers certain advantages over other methods of forming polymer layers, including, but not limited to, the ability to create thinner, more uniform polymer layers, a reduction of trapped gas within and/or under the polymer layer, greater density within the polymer layer, and a smoother finished surface.
The inventors of U.S. Pat. No. 5,681,615, incorporated herein by reference, later made the unexpected discovery that, when fully solvated, salts dissolved in monomer solutions may be evaporated along with the monomer according to the vacuum flash evaporation method and thereby used to form composite polymer layers under vacuum. In certain cases, however, particular salts or other substances of interest are not sufficiently soluble in the monomer to allow for flash evaporation. In addition, the technique disclosed in U.S. Pat. No. 5,681,615 patent requires the premixing of the monomer and the salt, thereby making it difficult to tailor the exact composition of the polymer composite layer.
The need therefore exists for an apparatus and method that allow for the creation of polymer composite layers via a flash evaporation process even in cases where the salt or other substance of interest is insufficiently soluble in the monomer of interest to allow for application of the technique disclosed in the '615 patent. The need also exists for an apparatus and method for tailoring more precisely the composition of polymer composite layers.